Piston assembly



May 14, 1935.. R. c. MCALLISITER PISTON ASSEMBLY Filed Nov. 15, 1934 I INVENTOR. 1210 dGMcHlliafeu wfiw A A x R 2 Q g ASK $0 r R g E. E.

Patented May 14, 1935 PISTON ASSEMBLY Raymond C. .McAllister, Painted Post, N. l[., as-

signor to Ingersoll-Rand Company, Jersey City, N. J., a corporation of New Jersey I Application November 15, 1934, Serial No. 753,129

6 Claims.

and held in assembled relationship with respect.

to each other by suitable devices.

The present invention is particularly'applicable to compressors intended for high pressure 'duty and wherein, it is'highlyessential that the several portions of the piston assembly be protected against binding strainssuch as might be caused by slightinaccuracies in alignmentof the cylinders in which the several portions of the piston assembly operate. I

i It is accordingly an object of the invention to enable the pistons of an assembled unit to adjust themselves laterally or angularly with respect to each other in order to prevent binding between them and the cylinders wherein they operate.

Other obects will be in part obvious and in part pointed out hereinafter.

The figure in the drawing is a longitudinal sectional elevation of a piston assembly constructed in accordance with the practice of the invention and showing it arranged within a compressor.

Referring more particularly to the drawing, 2!] designates, in general, a compressor comprising final and lower stage cylinders 2i and 22, respectively. The final stage cylinder 2! may, as illustrated, be supported by the cylinder 22 and contains a liner 23 of which the interior constitutes the final stage compression chamber 2 The admission of fluid into the chamber 24 is controlled by an inlet valve 25, and the discharge of the fluid compressed in the chamber 24 is controlled by a discharge valve 26. Likewise, the cylinder 22 is provided with inlet and discharge valves 21 and 28 to control the admission of fiuid into and the discharge of the compressed fluid from the cylinder 22.

The cylinders 2i and 22 are arranged coaxially with respect to each other and contains a piston assembly, designated in its entirety, by 29. The piston assembly comprises a piston 3i! in the cylinder 22 and a plunger 3! reciprocable in the compression chamber 24 and connected to the piston 30, to be actuated thereby. The plunger Si is provided, in its periphery, with a plurality of sealing rings 32 to minimize leakage from the chamber 24. The piston 39 maybe provided with similar sealing devices (not shown). i

In accordance with the practice of the invention, means are provided to enable the pistons to readily adjust themselves laterally or angularly in order to compensate for such slight degrees of disalignment as may result during the machining and assembling of the parts or as'a result of fluctuations in the temperature to which the cylinders and pistons are exposed. To this end a spacer 33 is interposed between the piston 39 and the plunger ii to seat against each or,as illustrated, against Wearing members 3% and 35 carried by the piston 39 and the plunger 3|, re 'spectively.

Preferably, the spacer 33 is of slightly smaller diameter than the plunger 3!, and on its ends are spherical surfaces 36 which seat against concave surfaces ii? on the wearing members a l and 35. The wearing member 34% consists of a plate which is secured to the piston 35 by bolts 38 and has a central projection 39 extending into a recess ii] in the piston'to centralize the wearing member with respect to the piston. The wearing member may conveniently consist of a cylindrical piece having a reduced stem ll seated in a recess 42 in the end of the plunger 3!.

Within the plunger 3i, the spacer 33 and the wearing members 3d and 35 are registering apertures 43 to receive a tie-rod M whereby these members are clamped together and secured to the piston 3i) to which one end of the tie-rod is threaded. The opposite end of the tie-rod is threaded, as at it, for the accommodation of a cap-nut 46. On the inner end ll of the nut 46 isa cone-shaped end which seats into a correspondingly shaped socket is of a plug 49 screwed into the adjacent end of the plunger 3! and having a cylindrical bore Edi, throughout a portion of its length, to engage the contiguous portion of the tie-rod M. The plug i9 is confined in the plunger 3! by a plate 5i secured to the end of the plunger, as by screws 52, and having an axial bore 53 through which the nut it extends.

Preferably the ends of the tie-rod M consist of up-set portions and the intermediate portion 5 of the rod M is thus of reduced diameter'to avoid contact thereof with the walls of the apertures 43.

In assembling the device the nut is is manipulated in such wise as to cause the various elements constituting the plunger M to seat firmly against each other while at the same time permitting angular adjustment of the spacer 33 with respect to the wear ng members 3 3 and 35. Thus, in the event that either the cylinders or the parts constituting the piston assembly become relatively disaligned the spacer 33 may readily shift itself angularly and permit each piston to assume a truly coaxial position with respect to its cylinder without binding on the walls of its cylinder.

Owing to the provision of clearance between the intermediate portion of the tie-rod and the walls of the apertures 43 these parts may readily adjust themselves without contacting with the intermediate portion of the tie-rod. Any deflection to which the tie-rod may be subjected will, therefore, be distributed along its entire length instead of localized.

I claim:

1. A piston assembly, comprising a plurality of pistons arranged in tandem, a spacer interposed between adjacent pistons to transmit the movement of one piston to another, cooperating spherical surfaces on the spacer and adjacent pistons to permit of relative angular disalignment of the pistons, and means connected to adjacent pistons to maintain the spherical surfaces in contacting relationship with each other.

2. A piston assembly, comprising a plurality of pistons arranged in tandem, a spacer interposed between adjacent pistons to transmit the movement of one piston to another, cooperating spherical surfaces on the spacer and adjacent pistons to permit of relative angular disalignment of the pistons, and means connected to corresponding ends of adjacent pistons to maintain the spherical surfaces in contacting relationship with each other.

3. A piston assembly, comprising a plurality of pistons arranged in tandem, a spacer interposed between adjacent pistons to transmit the movement of one piston to another, cooperating spherical surfaces on the spacer and the pistons to permit of relative axial disalignment of the pistons, and means within the pistons and the spacer to maintain the spherical surfaces in contacting relationship with each other.

4. A piston assembly, comprising a pair of coaxially arranged pistons, a spacer interposed between adjacent pistons to transmit the movement of one piston to the other, cooperating spherical surfaces on the spacer and the pistons to permit of relative disalignment of the pistons, and a rod in one piston and. the spacer connected to both pistons to maintain the spherical surfaces in contacting relationship with each other.

5. A piston assembly, comprising a pair of coaxially arranged pistons, a spacer interposed between adjacent pistons to transmit the movement of one piston to the other, cooperating spherical surfaces on the spacer and the pistons to permit of relative disalignment of the pistons, and a rod in the pistons and the spacer threadedly connected to the pistons to maintain the spherical surfaces in contacting relationship with each other and contacting with the encasing elements only at its extremities.

6. A piston assembly, comprising a pair of coaxially arranged pistons, a spacer interposed therebetween to transmit the movement of one piston to the other, wearing members on the confronting ends of the pistons, cooperating spherical surfaces on the wearing plates and. the spacer to permit of relative disalignment of the pistons, said piston, spacer and wearing members having coaxial apertures therein, and a rod extending through the apertures and being threadedly connected to the pistons to maintain the spherical surfaces in contacting relationship, said rod having an intermediate reduced portion to avoid contact thereof with the walls of the apertures.

RAYMOND C. MCALLISTER. 

